title: Glutathione reductase activity with an oxidized methylated glutathione analog.
abstract: The activity of glutathione reductase with an unnatural analog of oxidized glutathione was explored. The analog, L-γ-glutamyl-2-methyl-L-cysteinyl-glycine disulfide, places an additional methyl group on the alpha position of each of the central cysteine residues, which significantly increases steric bulk near the disulfide bond. Glutathione reductase was completely unable to catalyze the sulfur-sulfur bond reduction of the analog. Additionally, enzyme kinetics experiments indicated that the analog acts as a competitive inhibitor of glutathione reductase. Computational studies confirm that the methylated analog fits within the active site of the enzyme but its disulphide bond geometry is altered, preventing reduction by the enzyme. The substitution of (R)-2-methylcysteine in place of natural (R)-cysteine in peptides constitutes a new strategy for stabilizing disulphide bonds from enzyme-catalyzed degradation.
authors.affiliation: Department of Chemistry, University of Wisconsin Oshkosh , Oshkosh, WI , USA and.
authors.forename: Brant L
authors.initials: BL
authors.lastname: Kedrowski
authors.forename: Jonathan H
authors.initials: JH
authors.lastname: Gutow
authors.forename: Gorman
authors.initials: G
authors.lastname: Stock
authors.forename: Maureen
authors.initials: M
authors.lastname: Smith
authors.forename: Chondrea
authors.initials: C
authors.lastname: Jordan
authors.forename: Douglas S
authors.initials: DS
authors.lastname: Masterson
mesh_terms: D001667:Binding, Competitive / Q000187:drug effects; D055162:Biocatalysis / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D005978:Glutathione / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D005980:Glutathione Reductase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008745:Methylation; D008958:Models, Molecular; D008968:Molecular Conformation; D010084:Oxidation-Reduction; D013329:Structure-Activity Relationship
chemical_list: D005980:Glutathione Reductase; D005978:Glutathione
keywords: Computational chemistry; GSSG; disulfide reduction; enzyme kinetics; inhibition